Al-Kahf 18:21

And similarly, We caused them to be found that they [who found them] would know that the promise of Allah is truth and that of the Hour there is no doubt. [That was] when they disputed among themselves about their affair and [then] said, "Construct over them a structure. Their Lord is most knowing about them." Said those who prevailed in the matter, "We will surely take [for ourselves] over them a masjid